Step 1
The product here is H2SO3. Sulfur dioxide is dissolved in water to give solutions that contain sulfurous acid (H2SO3)
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Step 2
The reaction:
SO2 (g) + H2O (l) <=>H2SO3 (aq)
H2SO3 (aq) <=> H+ + HSO3- Ka1 (ionization constant)
HSO3- <=> H+ + SO3-2 Ka2
H2SO3 is a weak acid